Porous compositions



Y Patented Feb. 19, 1946 POROUS COMPOSITIONS Henry A. Gardner, ChevyChase, Md.

No Drawing. Application September 18, 1942, Serial No. 458,842

8 Claims.

This invention relates to a new composition of matter and a method ofmaking the same and to articles made from the new composition of matter.

It has been found that light-weight substances having valuable newproperties and a wide variety of useful applications may be obtained byreact ing a finely divided metal in substantial proportions with abinder composition capable of reacting with the metal with evolution ofa gas. The finely divided metal forms a substantial proportion of theresulting substance, preferably not substantially less than ten per centbut not substantially more than 50 per cent by weight thereof. Any metalor metal alloy capable of reacting in comminuted form with a suitablebinder substance, such as an acidic or acid-containing composition, withevolution of a gas, may be used, such as, for example, aluminum,magnesium, zinc, and iron. In general, however, metals of low specificgravity such as aluminum and magnesium result in compositions havingparticularly desirable properties.

The reactive binder substance is preferably a I material consisting ofor containing organic acids, such as shellac, rosin and other acidic oracid-containing natural resins, or synthetic plastic orresinoussubstances containing, for example, phthalic, malic, maleic andother acids, or their acid reaction products. The acidic bindersubstance may be utilized in solution or in liquid or semi-solidcondition.

The new compositions of the invention are porous, coherent substancescomprising a substantial portion of finely divided metal particlesbonded together by a binder substance reactive with the metal to producea gas and the reaction product of the metal and the binder substance. Ingeneral, it is believed that the reaction of the binder substance withthe metal particles not only produces a gaseous reaction product whichserves to form a multitude of pores in the final product, but alsoproduces a reaction productwith a portion of the metal whichsubstantially increases the binding efiect and contributes to thephysical characteristics of the final product.

In general, the products of the invention are lightweight, poroussubstances having a metallic appearance. Particularly when made ofmetals having a low specific gravity, they have a low apparent densityand readily float on water. The new products are typicallynon-conductors of electricity and have a high insulation power to heatfiow. The heat insulating properties of the substances due to theirporous structure may be very considerably enhanced when the metalparticles have a high reflecting power for'radiant energy in theinfra-red, such as aluminum powder. 7 a

The method of producing the new products will vary with the particularmetal and binder substance used, but, in general, the new materials maybe produced by mixing the finely divided metal and the reactive bindersubstance, and,

where necessary, heating or cooling the mixture to maintain atemperature at which the desired amount of gas is evolved undercontrollable conditions. The passing of a gas such as carbon di-. oxide,hydrogen or compressed air, into the reacting mixture is at timesadvantageous in producing a product of enhanced porosity.

The following examples are illustrative of the principles of theinvention:

Example 1 the mass will no longer pour.

If during the reaction the mass is placed in an oven at F., the reactiontakes place with greater violence, and in an hour or less it may becompleted.

The container is then unsealed and, if glass, it is broken to remove thesolid inside.

If the above ingredients are mixed in the above proportions and vacuumis used during the process, an even more speedy reaction takesplace.

If the alcohol used in the above mixture contains a small quantity, sayone per cent or less, of alkali such as sodium hydroxide in solution,the reaction becomes very violent. Neither heat norvacuum is requiredunder these conditions.

In any event, the product of the above reaction is in a solid form andhas a honeycomb structure. It appears to have most of thecharacteristics of metal, such as hardness, brilliancy of color,rigidity. It may be worked with tools. It floats upon water. It isinsoluble in the organic solvents, such as alcohol, which might havebeen used in the reaction mass. It is a non-conductor or electricity. Ithas an extremely low bulk 2 weight. It has unique sound absorbing andingasoline would leak if such tankwas riddled with sulatingcharacteristics. bullets.

when the reaction product of Example 1 was Example 2 100 parts by weightof phthalic anhydride are heated with one-half its molecular weight ofglycerin to a temperature of about 200 C. when reaction occurs andpartial esterification takes place. This clear water'white substance isthen allowed to cool to just above the point of solidiflcation, andthere is then stirred in the mass about 20 parts by weight of aluminumpowder. Reaction occurs and a puffy mass results. If during thisreaction a jet of warm air is passed through the mass, much more puflingcommand a honeycomb structure results.

Example 3 In reactions similar to those given in Examples 1 and 2,magnesium powder and zinc powder have been employed. The reactions withmagnesium. powder are extremely energetic. Those with zinc powder areless so. Nevertheless, somewhat similar metaloidaP' substances wereformed.

The; reaction may be carried out in molds shaped to produce usefularticles of manufacture or to produce pieces such as rods or slabs whichformed into a doughnut-shaped ring and covered with suitable fabric, itformed a very light, tough, waterproof product which could be used as alife preserver. It floats upon water and does not become water-logged.

At the present time huge tonnages of metallic lead are used for coatingelectric conduits and cables. The unique properties of metallic lead andits durability make it highly desirable for this purpose. I have found,however, that the After proper reaction there was formed within I thismetal chamber a solidified, honeycomb product having all thecharacteristics referred to above. It formed a vermin-proof, highlyinsulating door or side wall which could be used on refrigerators. Itsinsulating value appeared to be extremely high. It could therefore beused not only in refrigerators but for the side walls and roofs ofrailroad cars for transportationv of fruit, meats, and the like.

A miniature form was made, resembling the shape of an airplane wing.Into this form were placed a few rigid wire rods to serve asreinforcements. Ther was then poured into this area a mixture such as isdescribed in Example 1. After proper reaction, the forni was removed.There was produced, by this cold molding process, a solid airplane wingof excellent rigidity but of extremely light weight, with good strengthand otherdesirable physical properties. This wing will "float on water.It is believed that this process offers wide possibilities in the speedyproduction of airplane wings, in contrast with the slow, laboriousmethods now employed in the building of such wings with sheets of metalor with plywood. There could left in such wings spaces which could beutilized for holding gas tanks.

Because of the very porous nature of the material produced in Example 1,the space between the inner and outer shells of a small model of a gastank was filled with this material and the reaction carried out at atemperature of 140 F. The purpose of this was to produce a bullet-proofgasoline tank from which very little reaction product of Example 1 maybe used in place of lead for the abovepurpose. It forms an extremelyresistant,'waterproof covering for the cable wires. Fortunately, it hasthe unique property of being a non-conductor of electricity, whereasaluminum and most other metals are good conductors.

When a-pipe made of very thin side walls of steel metal or cellulosebase products is filled with the reaction product of Example 1, a rigidmember is formed, which is extremely light in weight but which has greatstrength. This would adapt this material for making struts and otherrigid members of aircraft.

When cardboard is formed into a cylindrical container in a double wallthickness, the space between the walls may be filled with the reactionproduct of Example 1, to add greatly to the strength of the container.

When the reaction products of Example 1 are; cast by cold molding intothe form of slabs, preferably about one inch thick and from 12 inchessquare up, a most unique product is produced. This product may be usedfor many purposes. It has very remarkable sound absorbing propertiesbecause of the unique structure of the ma-' terial. It may therefore beused very widely in the production of sound absorbing ceilings forofilces, factories, and other places.

It can also beused as a roofing material because of its very greatresistance to the conduction of heat or cold. Dwellings roofed with thisproduct would be warmer in winter and cooler in summer. "It could alsobe used in the production of flooring blocks to produce floors which aresound absorbing, tough, resistant to traffic, and

of a highly durable nature. It could also be pressed in the form ofsiding or shingles to produce extremely durable structural surfaceswhich would be waterproof, resistant to the transmission of heat orcold,'and sound absorbing. It could also be pressed into the form offurniture to produce extremely light weight furniture of good strength.

The reaction product of Example 1 may be cold molded in the form of pipewhich would be extremely light in weight and resistant tosoilconditions. Through pipe lines made of this materialcould be pumped oil,water, or other materials- I claim;

1. As an article of manufacture, a porous rigid asoaoos dielectricmetalloidal body characterized by a honeycomb structure and an apparentdensity less than that of water, said body containing a minor proportionnot less than about by weight of finely divided particles of a metal ofthe group consisting oi aluminum and magne-' sium bonded together withan acidic phthalic anhydride-glycerin resin binder including thereaction product of the metal with said acidic resin.

with an at least equal amount by weight or an acidic resin capable oireacting with the finely divided metal with evolution of a gas,confining sium bonded together with a shellac binder in-- cluding thereaction product of the metal with an acidic component of shellac.

4. As an article of manufacture,- a porous rigid dielectric metalloidalbody characterized by a the mixture within an enclosed space, andsubjecting the mixture, under conditions to accommodate pulling of thelatter, to a temperature at which said acidic resin reacts with aportion of said finely divided metal until the mixture is materiallyhoneycombed and solidified and vola-' tile ingredients substantiallyseparated from the solid product. v

'7. Process of making a rigid dielectric metalioidal body having ahoneycomb structure and an apparent density less than that of water,which comprises admixing 20 parts by weight of finely divided aluminumwith a partial esterification product or 100 parts of phthalic anhydridewith one-hall its molecular weight of glycerin,

- confining the mixture within an enclosed ce;

honeycomb structure and an apparent density weight of finely dividedaluminum particles bonded together with a shellac binder including thereaction product of the aluminum with an acidic component or shellac.

6. Process of making a rigid dielectric metalloidal body having ahoneycomb structure and an apparent density less than that of water,which comprises admixing finely divided metal 01' the group consistingor aluminum and magnesium and subjecting the mixture, under conditionsto accommodate puffing or the latteato a tempers= ture at whichsaidresin reacts with said ely divided aluminum until the mixture isaterl honeycombed and solidified and volatile .11; edients aresubstantially separated. from the solid product. I a

8. Process of making a rigid dielectricmetalloldal body having ahoneycomb structure and an apparent density less than that or water,which comprises admixing 20 parts by weight of finely divided aluminumwith about 20 parts by weight of shellac in fluid iorm, confining themixture within an enclosed space, and subjecting the mixture, underconditions to accommodate 'pufllng'oi the latter, to a temperature atwhich said shellac reacts with said finely divided aluminum until themixture is materially honeycombed and solidified and volatileingredients are substantially separated from the solid product.

HENRY A. GARDNER.

